This invention relates to an air filter for an internal combustion engine, especially for a motor vehicle, having a housing which has an air inlet at the raw air end and an air outlet at the clean air end, the air outlet being provided with a tubular nipple pointing into the interior of the housing and an annular filter insert being releasably fastened in the housing, wherein air flows radially through the filter insert from the outside in, and a radial gasket is provided on the end of the filter facing the tubular nipple, which engages the tubular nipple and seals the raw air chamber from the clean air chamber.
Published German Patent Application No. DE-OS 18 15 065 describes an air filter for an internal combustion engine, in which a filter insert is provided with a disk-shaped gasket which seals the raw air chamber from the clean air chamber. The gasket shown therein is fastened to the filter insert by providing a flange on one end disk of the filter insert, forming in combination with the end disk an annular groove into which the gasket is tightly fitted. When the filter insert is installed in the housing, this gasket slides along the inner wall of the housing until the filter insert has reached its installed position.
One disadvantage of this gasket is that, when the filter insert is installed, the gasket is severely deformed and bulges in the direction opposite the direction of installation. The result may be that, in the installed state, the reliable sealing of the clean air chamber will not be absolutely certain, and there is a danger that unfiltered air will enter the clean air chamber.
When an air filter is used in motor vehicles, vibrations of different frequencies must be expected. These vibrations can cause the air filter to enter into resonant vibration. In this case too the gasket must provide a reliable seal. In the known gasket, however, there is a danger that, due to the small effective sealing area and the gasket's low rigidity, seal problems may arise when subject to vibrations.
German Utility Model No. 19 34 075 furthermore discloses a combination of two cylindrical bodies provided with a gasket. The gasket there is provided with two sealing lips facing opposite sides. This gasket is intended to provide primarily for a reliable sealing of the two parts under varying pressure conditions.
A disadvantage of this known arrangement is that, particularly when the two parts to be sealed off from one another are assembled and disassembled, there is a danger that the gasket may roll up or be clamped between the parts and become damaged. Furthermore, the gasket is by its nature complicated to manufacture and therefore is not suitable for use in air filters.